1. Field of the Invention
This invention relates to an abrasive tape for use in polishing of a magnetic head for a magnetic recording and reproducing apparatus. This invention particularly relates to an abrasive tape for use in polishing of a magnetic head mainly by being moved between two reels in the manner of an ordinary magnetic tape.
2. Description of the Prior Art
Video or high grade audio magnetic heads are required to have very smooth tape sliding surfaces. Therefore, in general, in the process of making the magnetic head, the magnetic head is disposed at a predetermined position after being rough ground, and the tape sliding surface of the magnetic head is polished to a smooth finish by moving an abrasive tape between two reels disposed with the magnetic head intervening therebetween. The abrasive tape comprises a flexible non-magnetic substrate, and a coating film formed of fine abrasive grains, a binder, and an additive such as a lubricant and applied onto the non-magnetic substrate.
As the abrasive tape, there has heretofore been known, for exmaple, a cleaning tape as disclosed in Japanese Unexamined Patent Publication No. 53(1978)-102017, which comprises a substrate, and a coating film overlaid on the substrate and formed of abrasive grains consisting of zinc oxide (ZnO) or the like, a binder consisting of a vinyl chloride-vinyl acetate copolymer, a polyester polyol or the like, a curing agent consisting of a polyisocyanate or the like, and an additive such as silicone oil, which are kneaded together.
However, with the aforesaid cleaning tape, dispersibility of the abrasive grains is low, and the abrasive grains often agglomerate and concentrate locally in the cleaning tape, thereby causing scratching of the polished surface. Also, in the case of the abrasive tape, since it is desired to contain harder abrasive grains having a higher Mohs hardness than the abrasive grains used in the cleaning tape, more scratching arises when the dispersibility of the abrasive grains is low. Thus a need exists for an abrasive tape which can achieve polishing without scratching the polished surface even though hard abrasive grains providing a high abrasion efficiency are used.